I'm almost afraid to bring this up, because it's so controversial. But after homeschooling for 8 1/2 years and teaching in the public school system, I think this question has to be asked.
It's generally assumed that credentialing for teachers is very valuable. Liberals and conservatives, up to and including President Bush, advocate for teacher licensing. Every new president's education program seems to require more in terms of licensing for teachers. When a teacher has a teaching credential and specialization in their major, they are considered "highly qualified," and if they don't have the credential, they aren't. In Colorado, someone with a teaching credential is fairly easily able to add a new area of specialization - just take a test, or a few classes, or prove you've had some experience, and voila - you can teach it! But if you don't have a teaching credential, you may as well forget it - you must have that little piece of paper.
So what exactly do teachers have to study in order to get that piece of paper? I was planning to be a teacher for a while; I took the majority of the classes, in an excellent private university. We studied child development - material most of America learns by watching their children grow. We studied classroom management - how to get 30 kids to sit down, shut up, and listen. We studied motivation - how to get 30 kids interested enough that they actually learn something. We studied choosing curriculum - something most teachers don't get to do, because they are told which curriculum the school uses, and that's it. We studied lesson planning - something else teachers generally don't do a lot of since the textbook tells them what to do every day and they really don't have time to do anyway. And we learned a lot of technical jargon and contemporary learning theories, all of which are completely out-of-date and have been replaced by a lot of new technical jargon and new learning theories (and I graduated only 20 years ago).
Much of what teachers study is a waste of time. Most teachers learn to teach by experience and imitation. If they are fortunate, they have a positive experience and draw a good teacher to imitate; if not, they have to make the best of what they have. Many good teachers are already teachers at heart before they take a single class. Hours spent sitting in a classroom listening to lectures do not make a teacher; there is no substitute for actually teaching, a few kids at a time and eventually up to a whole class. And any kind of teaching or other leadership can make that happen - Sunday School, afterschool clubs, piano lessons, homeschool co-op groups, anything that requires the adult to lead groups of kids.
I'm not against teacher training; I'm against the bureaucracies that entrench requirements for classes like "Psychology Applied to Teaching." I'm against requiring a piece of paper rather than actual experience. I'm against a system that allows mediocre and even poor teachers into the classroom and eliminates excellent ones, simply because they haven't taken classes they don't need. I'm against judging the quality of teaching experience based on whether it happened in a school or in another context, and eliminating anything that didn't happen in a school. I'm against principals who don't help beginning teachers with potential, and experienced teachers who seem to think they are better simply because they've taken some classes. I'm against an education establishment who thinks they "paid their dues" so you should have to, too, and who judges the quality of a teacher and the value of their work based on how much technical jargon they can parrot back and whether they understand "contemporary learning theory" - whatever that happened to be when a particular teacher graduated from school.
Instead, I'm in favor of teachers being given guided experience. I'm in favor of teachers' knowledge being given as it's needed, rather than dumped on them before they can use it. I'm in favor of all teaching experience being taken into account. I'm in favor of principals providing support and training for their teachers, and more experienced teachers receiving bonuses for spending off-duty hours helping less experienced ones improve. I'm in favor of good teachers being paid based on their quality, not the number of years they've been there; and poor teachers being eliminated even if they've been teaching for years. I'm in favor of testing that is carefully designed to test the most important things - and then I'm in favor of teaching to that kind of test, and of judging teachers' performance based on that testing. I'm in favor of our kids being exposed to "the best of the best," that lets John Elway teach football and Paganini teach violin even if they haven't taken years of teacher training classes and student teaching.
The current teacher training system is just not working. I see no reason why we should be graduating high schoolers who can't read; why businesses should be complaining about not being able to find workers who meet basic minimum standards. Obviously the classes teachers are taking are not providing what they really need in the classroom. In the meantime, we are eliminating teachers who have years of experience teaching, who have great reputations and turn out excited and motivated students, and who are outstanding in their fields, simply because they don't have a piece of paper that says they've been trained to teach. We are requiring those teachers - who can make more money in the private sector - to take dozens of classes they don't need, and to be apprenticed under a "master teacher," who may not be as a good teacher as they are and for whom they will most likely end up grading papers for a semester, just so they can get that credential.
And what does the testing show about the need for those credentials? It shows that they provide no benefit whatsoever when it comes to results. Homeschooling students whose parents have credentials don't score any higher than those whose parents have a high school diploma. Students in public schools, whose teachers are required to have credentials, score lower than students in private schools, though their teachers often have no credentials at all, and lower than homeschooled students as well. Michael Smith has an interesting article on this subject, and on why high academic achievement among homeschoolers is so threatening to the education establishment. Essentially, his argument is that when homeschoolers do well, it destroys the fundamental assertion of so many education experts - that credentialling is not necessary to produce good teachers. And I think he's right.